See the cal BP discussion for additional information about radiocarbon calibration.

Tree-ring dating works because a tree grows larger--not just height but gains girth--in measurable rings each year in its lifetime.

In its most conventional form, dendrochronology works like this. They have no bias, and they have no political agenda; they just stand at locations all over the world," says Charlotte Pearson, an assistant professor of dendrochronology at the UA, studies samples under a microscope.

Environmental inputs into the cambium are primarily regional climatic variations, changes in temperature, aridity, and soil chemistry, which together are encoded as variations in the width of a particular ring, in the wood density or structure, and/or in the chemical composition of the cell walls.

At its most basic, during dry years the cambium's cells are smaller and thus the layer is thinner than during wet years.

To understand this process we must first understand a little bit about the atoms themselves and how they get their names.

Most carbon atoms have six positively charged protons and six uncharged neutrons.

Carbon-14 dating techniques were first developed by the American chemist, Willard F.